In the diagram below, AB is the chord of a circle with centre O. OM is perpendicular to AB (meet at a right angle). Look at triangles OAM and OBM. The hypotenuses (OA and OB) are the same ...

Segment: The area below the triangle formed by the sector is ... at the circumference of the circle. Perpendicular bisector of a chord always passes through the center of the circle.

Now use the information you already have about finding the equation of a line and apply it to the dashed lines shown in these triangles ... The perpendicular bisector passes through the midpoint ...